How many of our students come to the classroom with little background knowledge about the world around them and how things work? To help students develop conceptual understanding and explore the design process, the author brought the NASA "Engineering Design Challenges" program to his school district, redeveloped for elementary students. In this article, he describes how his fifth-grade students emulated NASA aerospace engineers as they designed and built Styrofoam and paper clip planes. (Contains 3 figures and 3 online resources.)